Wireless ic device system and method of determining authenticity of wireless ic device

ABSTRACT

An accessory device to be mounted on a main device is provided with a wireless IC device. The main device is provided with a reader/writer that is an interrogator that communicates with the wireless IC device of the accessory device. When the accessory device is mounted on or about to be mounted on the main device, the reader/writer selects two or more frequencies in a frequency band in which an authentic wireless IC device can communicate to perform communication with the wireless IC device. With this configuration, even if the identification code written in an RFID tag is read and the RFID tag is duplicated, the duplicated RFID tag can be accurately and effectively determined as being counterfeit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless IC device system thatdetermines the authenticity of an article by using an RFID tag and amethod therefor.

2. Description of the Related Art

Japanese Unexamined Patent Application Publication No. 2007-150642describes a wireless tag (RFID tag) that is used for physicaldistribution management and/or for authenticity determination. Thewireless tag of Japanese Unexamined Patent Application Publication No.2007-150642 was developed to solve a conventional problem in that sincethe frequency band in which communication is possible is narrow and thefrequency of a communicatable signal varies due to manufacturingvariations or the surrounding environment of the wireless tag,communication failure with an interrogator (reader/writer) occurs.Consequently, the wireless tag of Japanese Unexamined Patent ApplicationPublication No. 2007-150642 is configured such that authentication of anarticle is performed by changing the frequency of a signal using theinterrogator to find a frequency at which communication is possible.

FIG. 1 is a block diagram illustrating a configuration of a controllogic circuit 110 in the interrogator.

The control logic circuit 110 includes a PLL control section 301, atransmission signal generation section 302, a reception signalprocessing section 303, a transmission and reception control section304, a storage section (hopping channel-wireless tag ID storage table)305, and an external interface section 306.

The storage section 305 stores the relationship between a wireless tagID and a frequency changing channel (carrier frequency) to which thewireless tag responds. The PLL control section 301 controls carrierfrequencies.

Meanwhile, Japanese Unexamined Patent Application Publication No.2005-345802 discloses a configuration that includes an electronicequipment main body (camera) and a removable unit. The unit is providedwith an information communication chip that stores identificationinformation and other information, and an antenna. The electronicequipment main body (camera) includes an antenna and a device arrangedto read information, and further includes a controller arranged tocontrol operations with the unit based on read information.

RFID tags are normally provided on articles to determine authenticity.However, data written in an RFID tag can be read by analyzing the insideof the RFID tag, and thus, duplication of the RFID is technicallypossible. Even when the system described in Japanese Unexamined PatentApplication Publication No. 2007-150642 is used, the authenticationprocess is performed using only a certain frequency in a frequency bandin which communication is possible. Consequently, when a counterfeitwireless tag having the same identification code is attached to anarticle, the article is falsely determined to be authentic.

Further, in the wireless tag system described in Japanese UnexaminedPatent Application Publication No. 2007-150642, when a wireless tag isused that has a tuning frequency outside the range over whichcommunication is possible for the interrogator, there is a problem inthat trimming of the antenna pattern is required, thereby increasing thecost due to an increase in the number of processes.

Furthermore, in the device of Japanese Unexamined Patent ApplicationPublication No. 2005-345802, the electronic equipment initiates normaloperation even with a unit of an inferior imitation product if theidentification code of the RFID tag matches, whereby the electronicequipment main body may be damaged. Even if the identification code ofthe RFID tag of the removable unit is encrypted, the encryptionalgorithm and the encryption key can be determined by analyzing the IC,and thus, duplication/fabrication of the RFID is possible. Therefore,although the authentication determination using RFID tags may beeffective to prevent improper use, since encryption can be analyzedeasily in an environment in which proper consumable items as well aselectronic equipment main bodies are sold together, it is difficult tofully prevent improper use.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of thepresent invention provide a wireless IC device system that can, even ifthe identification code written in an RFID tag is read and the RFID tagis duplicated, accurately determine that the duplicated RFID tag iscounterfeit, and an authenticity determination method therefor.

A wireless IC device system according to a preferred embodiment of thepresent invention includes a wireless IC device for an RFID tag, and aninterrogator that communicates with the wireless IC device.

The interrogator preferably includes a circuit that randomly selects afrequency at which communication is to be performed from a frequencyband of the wireless IC device in which communication is possible tocommunicate with the wireless IC device, and a circuit that performsauthenticity determination of the wireless IC device by determiningwhether or not communication is possible at the frequency.

Compared with an authentic wireless IC device, a counterfeit RFID taghas a very narrow frequency band in which communication is possible.Therefore, with the configuration described above, communication isdisabled unless a randomly selected frequency incidentally matches afrequency at which the counterfeit RFID tag can communicate. Thisenables accurate authenticity determination of wireless IC devices.

The interrogator preferably selects two or more frequencies at whichcommunication is to be performed. With this configuration, it ispossible to accurately reject a counterfeit device in which multipletarget communication frequencies have been set in advance.

The frequency band of the wireless IC device and the interrogator inwhich communication is possible is preferably wider than a frequencyband that is used for the RFID tag, and authenticity determination isperformed by determining whether or not communication is possible at afrequency other than one included in the frequency band that is used forthe RFID tag.

For example, since frequencies used for RFID tags differ among Japan,Europe, and the U.S., authenticity determination is performed in Japanby attempting to use the interrogator to communicate with the RFID tagusing a frequency used for RFID tags in Europe, for example, and bydetermining whether or not the communication is possible at thefrequency.

With this configuration, when a frequency is randomly selected, afrequency at which a counterfeit RFID tag can communicate is notinadvertently selected, and thus, more secured authenticitydetermination is performed.

The interrogator is preferably provided on a main device, and thewireless IC device is provided on an accessory device that is connectedto or mounted on the main device.

The main device is preferably provided with a warning circuit thatissues a warning signal when it is determined in the authenticitydetermination that the wireless IC device is not authentic.

With this configuration, when the accessory device is mounted or aboutto be mounted on the main device, the authenticity of the accessorydevice is determined, whereby a counterfeit accessory device isprevented from being used.

The interrogator is preferably provided on a main device, and thewireless IC device is provided on an accessory device that is connectedto or mounted on the main device.

A circuit element is preferably provided that terminates or limits anoperation of the main device when it is determined in the authenticitydetermination that the wireless IC device is not authentic.

With this configuration, a counterfeit accessory device is effectivelyprevented from being used, and breakage and/or damage to the main deviceare also prevented.

The frequency band of the wireless IC device in which communication ispossible is preferably in a range of approximately five times toapproximately 1000 times that of a carrier frequency band of acommunication signal used by the RFID tag, for example.

With such a frequency band, even if the entire frequency band that theinterrogator may use is covered, at least five counterfeit RFID tags,each having a different communication frequency, are needed to beprovided on a counterfeit accessory device, and this is not realistic.Therefore, a deterrent effect on counterfeit tags is provided.

In a method of determining the authenticity of a wireless IC deviceaccording to a preferred embodiment of the present invention in which awireless IC device system including a wireless IC device for an RFID tagand an interrogator that communicates with the wireless IC device isprovided, a frequency at which communication is to be performed israndomly selected using the interrogator from a frequency band of thewireless IC device in which communication is possible to communicatewith the wireless IC device, and authenticity determination of thewireless IC device is performed by determining whether or notcommunication is possible at the selected frequency.

The interrogator preferably selects two or more frequencies at whichcommunication is to be performed.

The frequency band of the wireless IC device and the interrogator inwhich communication is possible is preferably wider than a frequencyband that is used for the RFID tag, and the authenticity determinationof the wireless IC device is performed by determining whether or notcommunication is possible at a frequency other than one included in thefrequency band that is used for the RFID tag.

According to various preferred embodiments of the present invention, thedetermination between authentic wireless IC devices and counterfeitwireless IC devices can be effectively and accurately performed.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a control logic circuit of an interrogatordisclosed in Japanese Unexamined Patent Application Publication No.2007-150642.

FIG. 2 is a block diagram of a system including a main device to which awireless IC device system according to a preferred embodiment of thepresent invention is applied and an accessory device thereof.

FIG. 3 is a block diagram illustrating respective configurations of awireless IC device and a reader/writer according to a preferredembodiment of the present invention.

FIG. 4 is a perspective view of the wireless IC device shown in FIG. 3.

FIG. 5 illustrates a layered structure of the wireless IC device shownin FIG. 3.

FIGS. 6A and 6B are an equivalent circuit diagram of the wireless ICdevice system having the wireless IC device shown in FIG. 3 and areflection characteristic diagram of the wireless IC device shown inFIG. 3.

FIG. 7 is a flowchart illustrating a processing procedure of a maindevice control circuit in the main device shown in FIG. 6A.

FIGS. 8A and 8B illustrate frequency bands for signals with which thewireless IC device and the reader/writer shown in FIG. 6A communicate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First PreferredEmbodiment

A wireless IC device system and a method of determining the authenticityof a wireless IC device according to a first preferred embodiment willbe described with reference to drawings.

FIG. 2 is a block diagram of a system including a main device 201 towhich a wireless IC device system according to the first preferredembodiment of the present invention is applied and an accessory device202 thereof. The accessory device 202 is provided with a wireless ICdevice 102. The main device 201 is provided with a reader/writer 101that is an interrogator that communicates with the wireless IC device102 of the accessory device 202.

The main device 201 and the accessory device 202 provide predeterminedfunctions when the accessory device 202 is connected to or mounted onthe main device 201. For example, when the main device 201 is a printer,the accessory device 202 is an ink cartridge. When the main device 201is a video game machine, the accessory device 202 is video gamesoftware, i.e., a cartridge, a disk, or other suitable software. Whenthe main device 201 is a DVD player, the accessory device 202 is DVDsoftware, i.e. a disk. When the main device 201 is a camera, theaccessory device 202 is an interchangeable lens thereof.

When the accessory device 202 is mounted or about to be mounted, themain device 201 determines whether the wireless IC device 102 is anauthentic wireless IC device (RFID tag), (hereinafter simply referred toas “real”, that is, the main device 201 determines whether the accessorydevice 202 including the wireless IC device 102 is real or counterfeit.

FIG. 3 is a block diagram illustrating respective configurations of thewireless IC device 102 and the reader/writer 101. In the reader/writer101, a communication control section 1 controls a wideband frequencyoscillation circuit 2 and a transmission signal encoding circuit 3 toinitiate communication or control the transmission of communicationsignals. That is, the wideband frequency oscillation circuit 2 outputsan oscillation signal to a frequency conversion transmission andreception circuit 5 and a modulation circuit 4 modulates a transmissionsignal frequency output from the frequency conversion transmission andreception circuit 5 in accordance with a data string output from thetransmission signal encoding circuit 3.

A wideband impedance matching circuit 6 matches the impedance betweenthe frequency conversion transmission and reception circuit 5 and asmall radiation plate 7 over a wide band. A transmission signal outputfrom the frequency conversion transmission and reception circuit 5 istransmitted as an electromagnetic wave from the small radiation plate 7via the wideband impedance matching circuit 6.

In addition, a modulation signal, which will be described later, fromthe wireless IC device 102 is demodulated by a demodulation circuit 8and a demodulation signal encoding circuit 9 converts the signal into adigital data string and provides it to the communication control section1. The communication control section 1 performs reading of theidentification code of the wireless IC device 102 and communicationcontrol based on the encoded data.

Meanwhile, in the wireless IC device 102, a small radiation plate 11receives the electromagnetic wave transmitted from the reader/writer 101and provides it as a power signal to a rectifier circuit 13 via awideband impedance matching circuit 12. The rectifier circuit 13rectifies the received electromagnetic wave, and a power supply controlcircuit 14 provides the voltage rectified by the rectifier circuit 13 asa power supply to a communication control section 15.

The communication control section 15 transmits based on data written toor having been written in advance in a memory 17, generates data, and,on the basis thereof, controls a transmission signal encoding circuit20. The transmission signal encoding circuit 20 drives a modulationcircuit 21 to modulate the electromagnetic wave transmitted from thereader/writer 101, and, after matching with the impedance of an externalspace is performed by the wideband impedance matching circuit 12, thetransmission signal encoding circuit 20 transmits the communicationsignal from the small radiation plate 11.

A demodulation circuit 18 demodulates the electromagnetic wavetransmitted from the reader/writer 101, and a demodulation signalencoding circuit 19 converts it into a digital data string and providesthe digital data string to the communication control section 15. Thecommunication control section 15 performs a predetermined communicationcontrol, such as returning the identification code, for example, on thebasis of the encoded transmission data from the reader/writer 101. As asecurity control circuit 16, a DES encryption circuit or an RSAencryption circuit, for example, is preferably used.

FIG. 4 and FIG. 5 illustrate a configuration of the wireless IC device102. This wireless IC device preferably includes a wireless IC chip 70that processes a transmission/reception signal of a predeterminedfrequency and a feeder circuit board 40 on which the wireless IC chip 70is mounted.

The feeder circuit board 40 is preferably defined by a multilayer board,as shown in FIG. 5, and preferably includes an inductance element L1, aninductance element L2 defining a radiation plate (loop antenna), andcapacitance elements C1 and C2.

In detail, the feeder circuit board 40 is preferably made by formingelectrodes described below on ceramic sheets 41A to 41N preferably madeof a dielectric material, for example, by a well-known method usingconductive paste or other suitable material, for example, and then bylaminating, bonding and firing these sheets 41A to 41N together.

That is, connection electrodes 35 a to 35 d and via electrodes 42 a and42 b are provided on and through the sheet 41A. A plane electrode 51(second plane electrode), conductor patterns 52 a and 52 b, and viaelectrodes 42 c, 42 d and 42 e are provided on and through the sheet41B. A plane electrode 53 (third plane electrode) and via electrodes 42c, 42 e and 42 f are provided on and through the sheet 41C. Conductorpatterns 45 a and 45 b and via electrodes 42 e, 42 f, 42 g, 42 h and 42i are provided on and through each of sheets 41D and 41E. A planeelectrode 54, conductor patterns 45 a and 45 b, and via electrodes 42 e,42 f, 42 h and 42 i are provided on and through the sheet 41F.

Further, conductor patterns 45 a and 45 b and via electrodes 42 e, 42 f,42 h and 42 i are provided on and through the sheet 41G. A planeelectrode 55, conductor patterns 45 a and 45 b, and via electrode 42 fare provided on and through the sheet 41H. Plane electrodes 56 and 57(referring the plane electrode 57 as a first plane electrode) and viaelectrodes 42 j and 42 k are provided on and through the sheet 41I. Aconductor pattern 46 and via electrodes 42 j and 42 l are provided onand through each of the sheets 41J to 41L. A conductor pattern 46 andvia electrodes 42 j and 42 m are provided on and through the sheet 41M.A conductor pattern 47 is provided on the sheet 41N.

By laminating the above sheets 41A to 41N together, the conductorpatterns 45 a and 45 b are preferably helically connected by the viaelectrodes 42 h and 42 i to define the inductance element L1, and theconductor patterns 46 are preferably helically connected by the viaelectrodes 42 l to define the inductance element L2 (radiation plate).One end of the inductance element L2 is connected to the plane electrode57 by the via electrode 42 k, and the plane electrode 57 faces theinductance element L1. The other end of the inductance element L2 isconnected to the plane electrode 56 by the via electrode 42 m, theconductor pattern 47, and the via electrode 42 j, and is furtherconnected to the plane electrodes 55 and 53 via the via electrode 42 f.The plane electrode 53 faces the plane electrode 51 to define thecapacitance element C1.

One end of the conductor pattern 45 a defining the inductance element L1is connected to the plane electrode 53 by the via electrode 42 c, theconductor pattern 52 a and the via electrode 42 d, and one end of theconductor pattern 45 b is connected to the plane electrode 54 by the viaelectrode 42 g. In addition, the other ends of the conductor patterns 45a and 45 b are integrated together on the sheet 41H, are connected tothe plane electrode 55, and are further connected to the connectionelectrode 35 a by the via electrodes 42 e, the conductor pattern 52 band the via electrode 42 a. The plane electrode 51 is connected to theconnection electrode 35 b by the via electrode 42 b.

The connection electrodes 35 a and 35 b are electrically connected toinput and output terminals of the wireless IC chip 70 preferably viametal bumps, for example. The connection electrodes 35 c and 35 d arepreferably terminating ground terminals and are connected to groundterminals of the wireless IC chip 70.

The inductance element L1 is preferably defined by helically arranging apair of the conductor patterns 45 a and 45 b parallel or substantiallyparallel to each other. The line lengths of the pair of the conductorpatterns 45 a and 45 b differ from each other, and thus, differentresonant frequencies are obtained, so as to increase the bandwidth ofthe wireless IC device.

In the wireless IC device 102, since both ends of the inductance elementL2 are electromagnetically coupled with a resonant circuit including theinductance element L1, impedance matching between the wireless IC chip70 and the radiation plate is performed through capacitances Cf betweenthe inductance element L1 and the wiring electrodes thereof, thecapacitance C1 between the electrode 51 and the electrode 53, and thecapacitances C2 between the electrode 54 and the electrode 53 andbetween the electrode 54 and the electrode 55. Consequently, variationsin the capacitances are small and variations in the frequencycharacteristic are also small. In addition, regardless of the impedanceof the wireless IC chip 70, the size and shape of the radiation platecan be set so as to obtain a predetermined radiation characteristic.

That is, this wireless IC device receives a high-frequency signalradiated from the reader/writer by the radiation plate and causes an LCresonant circuit (in terms of the equivalent circuit, an LC resonantcircuit defined by the inductance elements L1 and L2, the capacitanceelement C1 arranged between the plane electrodes 51 and 53, and thecapacitance element C2) to resonate to supply only a reception signalhaving a predetermined frequency band to the wireless IC chip 70.Meanwhile, predetermined energy is taken from this reception signal,and, by using this energy as a driving source, information stored in thewireless IC chip 70 is matched with a predetermined frequency using theLC resonant circuit, and then the information is transmitted to thereader/writer from the radiation plate.

Incidentally, the resonant frequency of the signal from the radiationplate is preferably set to a value greater than the resonant frequencyof the inductance element L1 and the usable frequency of the wireless ICdevice. Here, the resonant frequency of the signal from the radiationplate means the resonant frequency produced by the inductance element L2with capacitance elements C1 and C2. By using the radiation plate with afrequency not above the resonant frequency, a magnetic field isgenerated around the radiation plate, and thus, an electromagnetic wavecan be transmitted to a dielectric material, such as resin, for example,at the location at which the wireless IC device 102 is attached. Whenthe electromagnetic wave is radiated to the dielectric material,reflection occurs at a portion where the dielectric constant differs,i.e., between the wireless IC device 102 and the dielectric material,and the wave is transmitted to the outside. Therefore, the wireless ICdevice 102 can be used in an RFID system by being attached to orembedded in a predetermined surface of the accessory device 202.

In addition, since the first plane electrode 57 connected to one end ofthe radiation plate is arranged so as to face the inductance element L1,a magnetic field generated at the inductance element L1 is radiated tothe plane electrode 57, causing an eddy current in the plane electrode57. The eddy current flows into the radiation plate to generate amagnetic field in the radiation plate, whereby transmission or receptionis performed between the radiation plate and the reader/writer. In thismanner, the plane electrode 57 interrupts the magnetic field generatedat the inductance element L1. Therefore, configuring the radiation plateinto a shape so as to transmit and receive high-frequency signals havinga predetermined frequency improves the design flexibility oftransmission/reception signals for the wireless IC device. In addition,configuring the plane electrode 57 so as to be larger than the occupancyarea of the plane electrode 57 improves the interruption effect of themagnetic field of the inductance element L1, and thus, the designflexibility is further increased so as to improve the radiationcharacteristic.

Further, since a large capacitance coupling through the capacitanceelement C1 occurs between the plane electrode 53 connected to theradiation plate and the plane electrode 51, impedance matching of thewireless IC chip 70 with the radiation plate can be performed throughthe capacitance element C1. Furthermore, since the wireless IC chip 70is not directly electrically conductive with the radiation plate, damageto the wireless IC chip 70 due to static electricity having an energywave of about 200 MHz or less entering from the radiation plate isprevented.

Moreover, a stray capacitance Cf is generated between the wiringelectrodes defining the inductance element L1. This stray capacitance Cfalso affects impedance matching or the resonant frequency. However, bysetting the capacitance of the capacitance element C1 defined by theplane electrodes 51 and 53 to a large value, effects of variations inthe stray capacitance Cf due to variations in the spacing between thewiring electrodes are reduced, whereby variations in the usablefrequency are further reduced.

In addition, since the feeder circuit board 40 is preferably defined bya multilayer board, the inductance element L1 and the inductance elementL2 can be provided on layers inside the multilayer board, whereby thesize of the feeder circuit board 40 is reduced.

Note that although in the arrangement shown in FIG. 5, the planeelectrode 53 connected to the radiation plate and the plane electrode 51are preferably capacitively coupled, both plane electrodes may,alternatively, be directly electrically conductive with each other. Insuch a case, impedance matching is performed through the inductanceelement L1 and the stray capacitance Cf between the wiring electrodes.

Next, an equivalent circuit of the wireless IC device system including awireless IC device described above and a reflection characteristic ofthe wireless IC device are shown in FIGS. 6A and 6B.

In the equivalent circuit shown in FIG. 6A, two inductance elements L1 aand L1 b provided in the feeder circuit board 40 of the wireless ICdevice 102 correspond to the inductance element L1 shown in FIG. 5.These two inductance elements L1 a and L1 b preferably have differentinductance values and, thus, peaks occur at respective resonantfrequencies, whereby the reflection characteristic in which the band ofthe usable frequency is widened, as shown in FIG. 6B, is obtained.

The wireless IC chip 70 preferably includes a radio frequency IC (RFIC)in which a high-frequency circuit is provided and a baseband IC in whicha logic circuit is provided.

Similarly, the reader/writer 101 preferably includes a feeder circuitboard 62. The feeder circuit board 62 has a similar configuration to thefeeder circuit board 40 of the wireless IC device 102, whereby awideband characteristic is achieved. A reader/writer control circuit 61preferably includes, as in the case with the wireless IC chip 70 of thewireless IC device 102, an RFIC in which a high-frequency circuit isprovided and a baseband IC in which a logic circuit is provided. A maindevice control circuit 60 controls the reader/writer 101, and also readsthe identification code of the wireless IC device 102 and performs aprocess based on the result.

Note that, if a UHF band is used, communication is preferably performedby a radiation electromagnetic field method, that is, by transmissionand reception of electromagnetic waves. If an HF band is used,communication is preferably performed by an electromagnetic couplingmethod, that is, by transmission and reception of magnetic fieldsignals.

FIGS. 8A and 8B are diagrams illustrating frequency bands for signalswith which the wireless IC device 102 and the reader/writer 101communicate. Where the wireless IC device 102 is used as an RFID tag fora UHF band, the frequency band is preferably set so as to obtain a gainover a wide band from about 800 MHz to 1.2 GHz, for example, as shown inFIG. 8A. Where the wireless IC device 102 is used as an RFID tag for anHF band, the frequency band is preferably set so as to obtain a gainover a wide band from about 5 MHz to about 30 MHz, for example, as shownin FIG. 8B.

Part 3 and Part 6 of ISO/IEC 18000 respectively define the RFID airinterface at about 13.56 MHz and that at UHF band frequencies. For theUHF band, about 953.5 MHz±2 MHz is used in Japan, about 866.6 KHz±1 MHzis used in Europe, and about 915 MHz±13 MHz is used in the U.S.

Thus, it is sufficient to have a maximum frequency band of about ±20 MHzfor communication signals used by RFID tags for the UHF band. For anormal RFID tag supporting only conventional predetermined frequencies,the frequency band can be achieved by using, for example, an antennahaving the dimensions of about 5 nm×about 5 nm. For a counterfeit RFIDtag, a configuration is provided such that communication is possible ina band of, for example, about 953.5 MHz±2 MHz, or a configuration isprovided such that communication is possible in a band of, for example,about 13.56 MHz±28 kHz. On the other hand, the wireless IC device 102for a real RFID tag can communicate over a wide band from about 800 MHzto about 1.2 GHz, for example. In addition, the same wireless IC devicefor the RFID tag can be used around the world without modification, andthus, there is no need to tune the wireless IC device to a frequency foreach shipment destination, whereby the cost of the wireless IC device issignificantly reduced.

Note that, when, for example, video game software is placed in a videogame machine, the distance between the interrogator and the RFID tag isapproximately a few millimeters. Since communication is performed acrosssuch a small distance, a radio used in the RFID tag may be a specifiedlow power radio of about 10 mW or less. Therefore, authenticitydetermination is enabled in communication in which a limitation offrequency band is not necessary.

Furthermore, since both of the wireless IC device for the RFID tag andthe interrogator according to a preferred embodiment of the presentinvention can be used over a wide band and applied around the worldwithout modification, when authenticity determination is performed usinga frequency band that is not used in a certain area, a frequency atwhich a counterfeit RFID tag can communicate is not in advertentlyselected, and thus, more secured authenticity determination can beperformed.

For example, communication may be performed using a frequency in thefrequency band of about 866.6 KHz±1 MHz used in Europe or using afrequency in the frequency band of about 915 MHz±13 MHz used in theU.S., other than the frequency band of about 953.5 MHz±2 MHz assignedfor RFID tags used in Japan, to perform authenticity determination bydetermining whether or not the communication has been successful.

FIG. 7 is a flowchart illustrating a processing procedure of the maindevice control circuit 60 shown in FIG. 6A.

First, a mounting state of the accessory device 202 is detected (S1).This is performed by, for example, reading the state of an accessorydevice mounting state detection switch provided on an accessory devicemounting section of the main device 201.

When the accessory device is mounted, a variable N for counting thenumber of repetitions, which will be described later, is initialized(S2), and a random number is generated (S3). Then, a carrier frequencycorresponding to the generated random number is determined (S4). For anRFID tag using a UHF band, the frequency band from about 800 MHz toabout 1.2 GHz is divided into channels preferably having a band width,for example, of about ±5 MHz, as shown in FIG. 8A, and thus, theselection of 40 channels ((1200−800)/10=40 channels) are available, andan interrogation signal is transmitted from the reader/writer at thecarrier frequency of one of the 40 channels in accordance with therandom number (S5). For an RFID tag using an HF band, the frequency bandfrom about 5 MHz to about 30 MHz is divided into channels preferablyhaving a band width, for example, of about ±28 kHz, as shown in FIG. 8B.In this manner, the reader/writer 101 attempts to communicate with thewireless IC device 102 at a communication frequency which has beenrandomly selected.

Although frequencies of 40 channels are preferably used as describedabove, it is sufficient to use frequencies of at least 5 channels. Thatis, a frequency band in which an authentic wireless IC device cancommunicate is preferably not less than approximately five times thecarrier frequency band of communication signals used in RFID tags. Withthis configuration, at least five counterfeit RFID tags, each having adifferent communication frequency, must be provided on a counterfeitaccessory device, and this is not realistic. Therefore, a deterrenteffect on counterfeit tags is effective.

A response signal from the wireless IC device (RFID tag) 102, if any, isreceived and a determination is made as to whether or not the responsesignal is a correct identification code (S6 to S7). If theidentification code is normal, the counter N value is incremented byone, and then the processes from steps S3 to S9 are repeated (S8 to S9to S3 . . . ).

The processes described above are repeated five times, that is, if thewireless IC device can perform communication in response tointerrogation signals of all five different carrier frequencies andnormal identification codes are replied, then normal processes areinitiated (S8 to S10). Although switching is preferably performed amongfive frequency bands, for example, the determination may be made as towhether or not communication is possible with at least two differentfrequencies.

If normal identification codes are not replied in the communication withfive different carrier frequencies, it is determined that the wirelessIC device provided on the accessory device is counterfeit, that is theaccessory device is counterfeit, and a warning is provided to the user.For example, a warning sound is made or a warning display is provided toindicate that the accessory device is counterfeit (S7 to S11).

After that, the power supply of the main device is interrupted and theprocessing is completed (S12). In this manner, mounting of a counterfeitaccessory device is effectively and accurately detected and operationsusing the counterfeit accessory device are prevented.

Note that although in the preferred embodiment described above, when acounterfeit accessory device is mounted or about to be mounted, awarning is generated and then the power supply of the main device isinterrupted to terminate the operation completely, for example, the maindevice may enter a limited operation mode, such as a mode in which anoperation that uses an accessory device is disabled.

In the preferred embodiment described above, a band from about 800 MHzto about 1.2 GHz, for example, is preferably supported since an RFID tagusing a UHF band is used. However, from a practical standpoint,communication over a wider band from about 800 MHz to approximatelyabout 5 GHz is possible. In such a case, (5000−800)/10=420 channels areavailable, if the frequency band of communication signals of RFID tagsis about 10 MHz, or (5000−800)/4=1050 channels are available, if thefrequency band of communication signals is about 4 MHz. Consequently, afrequency band in which communication is possible for an authenticwireless IC device is preferably less than approximately 1000 times thecarrier frequency band of communication signals used in RFID tags, forexample.

As described above, according to a preferred embodiment of the presentinvention, fabrication can be preventing by the following two majorbarriers.

First, even when analysis of the wireless IC device for the authenticRFID tag according to a preferred embodiment of the present invention isattempted for fabrication, it is extremely difficult to perform theanalysis by detecting a communication signal using digital technologysince the frequency of an interrogation signal from the reader/writer isnot constant. This is the first barrier.

In addition, even if the encryption algorithm or the identification codeis analyzed by analyzing the bit pattern of the IC chip and the bitpattern is duplicated, the analysis and duplication are successful onlyfor a baseband portion. Since the frequency band in which communicationis possible for a counterfeit RFID tag should have been set to apreliminarily standardized frequency band, it is impossible to respondto an interrogation signal of frequencies in a wide band withoutmodification. This is the second barrier.

Note that, the main device 201 preferably including the reader/writer101 is described above. However, only a reader (interrogator) may beprovided when there is no need to write data to a memory in the wirelessIC device for an RFID tag.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing the scope andspirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

1. A wireless IC device system comprising: a wireless IC device for anRFID tag; and an interrogator arranged to communicate with the wirelessIC device; wherein the interrogator includes a circuit arranged torandomly select a frequency at which communication is to be performedfrom a frequency band of the wireless IC device in which communicationis possible to communicate with the wireless IC device, and arranged toperform authenticity determination of the wireless IC device bydetermining whether or not communication is possible at the frequencyselected by the interrogator.
 2. The wireless IC device system accordingto claim 1, wherein the interrogator includes a circuit arranged toselect at least two frequencies at which communication is to beperformed.
 3. The wireless IC device system according to claim 1,wherein the frequency band of the wireless IC device and theinterrogator in which communication is possible is wider than afrequency band that is used for the RFID tag, and the randomly selectedfrequency is a frequency other than one included in the frequency bandthat is used for the RFID tag.
 4. The wireless IC device systemaccording to claim 1, wherein the interrogator is provided on a maindevice, and the wireless IC device is provided on an accessory devicethat is connected to or mounted on the main device; and the main deviceincludes a warning circuit arranged to provide a warning when it isdetermined that the wireless IC device is not authentic.
 5. The wirelessIC device system according to claim 1, wherein the interrogator isprovided on a main device, and the wireless IC device is provided on anaccessory device that is connected to or mounted on the main device, andan operation control unit is arranged to terminate or limit an operationof the main device when it is determined that the wireless IC device isnot authentic.
 6. The wireless IC device system according to claim 1,wherein the frequency band of the wireless IC device in whichcommunication is possible is in a range of approximately five times toapproximately 1000 times a carrier frequency band of a communicationsignal used by the RFID tag.
 7. A method of determining an authenticityof a wireless IC device in a wireless IC device including a wireless ICdevice for an RFID tag and an interrogator that communicates with thewireless IC device, the method comprising the steps of: randomlyselecting using the interrogator a frequency at which communication isto be performed from a frequency band of the wireless IC device in whichcommunication is possible to communicate with the wireless IC device;and performing authenticity determination of the wireless IC device bydetermining whether or not communication is possible at the frequencyselected in the selecting step.
 8. The method of determining theauthenticity of a wireless IC device according to claim 7, wherein theinterrogator selects at least two frequencies at which communication isto be performed.
 9. The method of determining the authenticity of awireless IC device according to claim 7, wherein the frequency band ofthe wireless IC device and the interrogator in which communication ispossible is wider than a frequency band that is used for the RFID tag;and the authenticity determination of the wireless IC device isperformed by determining whether or not communication is possible at afrequency other than one included in the frequency band that is used forthe RFID tag.